UV-curable waterborne polyurethane dispersions for soft touch coatings

Abstract

The present invention is directed to a waterborne, UV-curable polyurethane emulsion and the use thereof in producing soft touch coatings. The emulsion is prepared by a) reacting specified hydroxy-functional components with di- and/or polyisocyanates, b) forming a dispersion of the resultant product with water and reacting the dispersion with amine functional materials.

1. A radiation-curable, aqueous polyurethane emulsion prepared by a process comprising:
 A) reacting 
 1) from about 5 to about 45% by weight of an hydroxy group containing, unsaturated polyester acrylate having an OH number of from about 40 to about 200, 
 2) from about 5 to about 60% by weight of a polycarbonate diol having an OH number of from about 28 to about 225, 
 3) from about 10 to about 20% by weight of a polyether diol having an OH number of from about 28 to about 225, with the proviso that if component 3) is present, the weight ratio of component 2) to component 3) is from about 0.5:1 to about 25:1, 
 4) from about 2 to about 8% by weight of a monohydroxy hydrophilic polyether, 
 5) from about 1 to about 8% by weight of one or more mono- or difunctional isocyanate-reactive compounds that contain moieties selected from cationic groups, anionic groups, potential cationic groups and potential anionic groups, with 
 6) from about 10 to about 30% by weight of one or more diisocyanates and/or polyisocyanates, 
 B) optionally converting any potential cationic or anionic groups into cationic or anionic groups by salt formation, and 
 C) forming a dispersion of the reaction product of 1), 2), 3), 4), 5) and 6) in water and reacting said dispersion with 
 7) from about 0.1 to about 3% by weight of one or more diamines and/or polyamines, 
 wherein the weight percents of components 1) through 7) total 100% and the equivalent ratio of the isocyanate groups in component 6) to the sum of the isocyanate-reactive groups in component 1), 2), 3), 4) and 5) is from about 1.2:1 to about 2.0:1. 
 
     
     
       2. The emulsion of  claim 1 , wherein components 1) through 7) are reacting in the following amounts:
 component 1) from about 20 to about 30% by weight, 
 component 2) from about 30 to about 40% by weight, 
 component 3) from about 10 to about 15% by weight, 
 component 4) from about 3 to about 5% by weight, 
 component 5) from about 2 to about 4% by weight, 
 component 6) from about 13 to about 23% by weight and 
 component 7) from about 0.5 to about 2% by weight. 
 
     
     
       3. The emulsion of  claim 1 , wherein the weight ratio of component 2) to component 3) is from about 3:1 to about 5:1. 
     
     
       4. The emulsion of  claim 3 , wherein the weight ratio of component 2) to component 3) is from about 3:1 to about 4:1. 
     
     
       5. The emulsion of  claim 1 , wherein said equivalent ratio is from about 1.4:1 to about 1.6:1. 
     
     
       6. The emulsion of  claim 1 , wherein the OH number of component 1) is from about 100 to about 200, the OH number of component 2) is from about 28 to about 75 and the OH number of component 3) is from about 28 to about 75. 
     
     
       7. The emulsion of  claim 6 , wherein the OH number of component 1) is from about 125 to about 180, the OH number of component 2) is from about 35 to about 65 and the OH number of component 3) is from about 35 to about 65. 
     
     
       8. The emulsion of  claim 1  further comprising from 0 up to 80% by weight based on the weight of components 1) through 7) of materials selected from the group consisting of acrylate terminated urethanes, arcylate terminated polyesters, acrylate terminated polyethers, acrylate terminated polycarbonates, methacrylate terminated urethanes, metharcylate terminated polyesters, methacrylate terminated polyethers, methacrylate terminated polycarbonates, and mixtures thereof. 
     
     
       9. The emulsion of  claim 8  wherein said material is present in an amount of from about 10 to about 15% by weight. 
     
     
       10. The emulsion of  claim 1  additionally comprising from about 0.1 to about 10% by weight, based on the weight of components 1) through 7), of one or more photo-initiators. 
     
     
       11. The emulsion of  claim 10  wherein said photo-initiator is present in amount of from about 3 to about 7% by weight. 
     
     
       12. The radiation cured coated prepared from the emulsion of  claim 1 . 
     
     
       13. In a method of prepared a cured coating by applying a coating composition to a substrate and curing the composition by UV radiation, the improvement wherein the composition is the emulsion of  claim 10 . 
     
     
       14. The product produced by the process of  claim 13 .